An ink jet recording apparatus (hereinafter referred to also as an ink-jet printer) enables high speed recording with low noise and makes it easy to form a color image by employing plural ink nozzles. Recently, the ink-jet recording printer is rapidly spreading as an image formation output apparatus for a computer.
Further, an ink-jet printer developed for a full color recording can record, on a transparent film or glossy resin-covered paper, a high quality color image corresponding to a photographic image according to photographic procedure, and record characters, figures, a color original or design image in which a high quality image corresponding to a photographic image is required.
As Ink for ink jet recording, a water based ink having, as main components, water and a water soluble organic solvent has been used in view of safety or recording properties, so that ink clogging of nozzles is minimized. As a recording sheet used for ink-jet recording system, conventionally, paper or a recording sheet referred to as an ink-jet recording paper wherein a porous ink receiving layer is provided on a support has been used.
However, the above-mentioned ink-jet recording sheets result in much ink blurring and low glossiness, and could not be employed for the above-mentioned field wherein high quality image is required. The porous ink absorbing layer coated on a glossy resin-covered paper has a rough surface and causes light scattering, resulting in the problem that transparency and glossiness are lowered. The non-porous ink receiving layer increases light transmittance, but there was the problem that ink after ink recording remains without being dried on the surface for a long time, and requires a long drying time.
In order to overcome the above-mentioned problems, there is proposed a water soluble polymer containing ink receiving layer swelled or dissolved by a water based ink. For example, an ink receiving layer comprised of gelatin having a specific pH is proposed in Japanese Patent O.P.I. Publication No. 62-263084, an ink-jet recording sheet, which is obtained by coating a gelatin layer on a support to be in gel state and then drying it by a cold drying method, is proposed in Japanese Patent O.P.I. Publication No. 6-64306, and an ink receiving layer containing polyethylene oxide with an average molecular weight of 5-10.sup.4 or more is proposed in Japanese Patent O.P.I. Publication No. 62-214985.
In order to obtain water resistance property to an ink receiving layer, use of a cross-linking agent is proposed. For example, an ink receiving layer comprised of polyvinyl alcohol with a saponification degree of 50 to 90 mol % and its cross-linking agent is proposed in Japanese Patent O.P.I. Publication No. 60-234879, and an ink receiving layer comprised of barium sulfate, gelatin and a gelatin hardener is proposed in Japanese Patent O.P.I. Publication No. 3-2114873.
In the ink receiving layer comprised of a specific water soluble polymer and a specific cross-linking agent as in the above literatures, ink absorption or water resistance is improved to some degree, but the ink absorption is not necessarily satisfactory. When printed at high speed and high resolving power by a printer jetting a large amount of jetting ink, the above mentioned techniques produce density unevenness or streak unevenness due to ink aggregation caused by insufficient ink absorption, resulting in poor image quality, and the jetting ink remains undry on an ink receiving layer for a long time.
When printed employing a specific ink-jet printer and a specific ink with high ink jetting amount, it has been proved that only the above mentioned techniques produce image blurring under high humidity and markedly lower image light fastness.